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<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    // const PI = 3.14
    // PI = 3.1415
    // console.log(PI)

    const obj = {
      name: 'jack',
      age: 18
    }
    // 错误的
    // obj = []
    obj.age = 99
    obj.name = 'rose'
    console.log(obj)
  </script>
</body>

</html>